In hierarchical computer storage systems, fast and intensively used storage are paired with arrays of slower and less frequently accessed data devices. One example of high-speed, expensive memory is a direct access storage device file buffer (DASD). Slower storage devices include tape drives and disk drive arrays, which are less expensive than a DASD.
Data disaster recovery solutions include various “peer-to-peer” copy routines where data is backed-up not only remotely, but also continuously (either synchronously or asynchronously). In order to communicate duplexed data from one host processor to another host processor, or from one storage controller to another storage controller, or some combination thereof, a substantial amount of control data is required for realizing the process. A high overhead, however, can interfere with a secondary site's ability to keep up with a primary site's processing, thus threatening the ability of the secondary site to be able to recover the primary in the event a disaster occurs.
Disaster recovery protection for the typical data processing system requires that primary data stored on primary DASDs be backed-up at a secondary or remote location. The physical distance separating the primary and secondary locations can be set depending upon the level of risk acceptable to the user, and can vary from several kilometers to thousands of kilometers.
In order to assure data consistency at both the primary information storage and retrieval system and the secondary information storage and retrieval system, particularly when using an asynchronous PPRC copy methods, it is desirable to communicate information expeditiously from the primary storage system to the secondary system.
Applicants' method evaluates one or more established communication pathways interconnecting a primary information storage and retrieval system with a remote information storage and retrieval system, identifies functional communication pathways, and, initially, sequentially attempts a single information transfer using each of those functional communication pathways until information transfer is successful. If information transfer is not successful using the known functional pathways, Applicants' method then selects an established communication pathway to transfer the information using a retry algorithm which, if the communication pathway is not stable, waits a prescribed period of time to allow the pathway to stabilize, and then makes one attempt to transfer the information using each selected established pathway.